Recent advances in technology have increased the demand for improved nanocomposite material processing with strict tolerances on processing parameters. For example, current integrated circuit technology already requires tolerances on processing dimensions on a submicron scale. Self-assembly approaches have been developed for the fabrication of very thin films of composite materials. These self-assembly processes, however, while highly advantageous, generally are limited with respect to the types of materials that can be deposited by a particular process, by costs and manufacturing facilities.
Presently, nanocomposite materials are manufactured in large manufacturing facilities that are expensive to build and to operate. For example, semiconductor device fabrication generally requires specialized microlithography and chemical etching equipment as well as extensive measures to avoid process contamination. Furthermore, the fabrication processes typically used to create electronic and electromechanical components involve harsh conditions, such as high temperatures and/or caustic chemicals. In addition, high temperatures also preclude fabrication on substrates such as flexible plastics, which offer widespread availability and lower costs.
Presently, there is a serious drawback associated with using polymer materials in the thin film due to their susceptibility to marring and scratching by physical contact with harder materials. Continuous marring and scratching result in impaired visibility and poor aesthetics, and often requires replacement of the plastic components.
Several techniques to improve the abrasion wear resistance of plastic substrates use coating solutions which may be spread onto the desired plastic substrates by dip, spray, spin, or flow techniques. The resulting coatings generally offer significant improvement of abrasion-resistance, but generally exhibit flow marks on the surface and an uneven coating thickness distribution that may cause undesirable optical aberrations.
Other techniques for forming abrasion-resistant coatings involve spin dip, spray or flow methods to form abrasion resistant coatings on smooth surfaces such as optical elements in spectacle lenses. The build-up of the coating material at the outer edge of the lens, however, can cause optical aberration. These techniques are even less satisfactory when they are used to coat irregular surfaces. Moreover, the application of many of the prior abrasion resistance coatings require thermally activated initiators so the plastic substrates must be exposed to elevated temperature in order to fully develop the physical properties of the coating and to remove the solvents. Such high temperature processing may significantly degrade the quality of the plastic, through the incorporation of residual stresses.
Vapor deposition techniques for coating application have also been employed. The technique typically involves the vapor deposition of a top layer of silicon dioxide onto an intermediate layer of an acrylate-type polymer that has, in turn, been coated onto a polycarbonate substrate. This evaporative technique of applying a layer of silicon dioxide, however, is often undesirable for several reasons, including (i) insufficient bond strength between the silicon dioxide layer and the underlying polymer layer, (ii) the resulting non-uniform surface is often characterized by pinholes, pits, and other imperfections, (iii) the difficulty to obtain uniformly thick coatings on curved or irregular or large-size substrates, (iv) the significant degradation of the plastic due to its exposure to high temperature, and (v) the spalling and cracking that occurs when the film thickness is increased beyond approximately 0.5 micrometer.
Accordingly, it is one object of the present invention to provide methodologies to lessen the disadvantages associated with the fabrication of nanocomposite materials.